LSD, lysergic acid diethylamide or lysergide, is a partial agonist at central type 5-HT_2A receptors, with usually low toxicity relative to other psychoactive drugs in normal doses.¹⁹

A small study of 16 healthy volunteers found that subjective dose-dependent effects started at a dose of 25 microgrammes. ‘Good’ effects due to LSD would be reported with a dose up to 100 microgrammes, but then plateaued, while doses of 200 microgrammes saw more ego dissolution (the loss of a sense of self-identity distinct from the rest of the world) and increased anxiety. Other effects were increased blood pressure and increased heart rate.^20,21

Global data on recreational use suggests that around 1% of LSD users sought emergency treatment, mainly for panic, anxiety and confusion. While most returned to normal after 24 hours, around 10% of those seeking medical treatment for an adverse LSD effect reported experiencing persistent issues after four weeks.¹⁹

Around 2% of users report that LSD has had a negative effect on their well-being. Frank, the independent UK-government funded website giving “honest information about drugs”, warns that LSD can make mental health problems worse, and people have been known to harm themselves during a bad trip.^19,22